Acne afflicts 90% of all teenagers but also men and women in their twenties or thirties or may persist throughout adulthood. The process by which acne develops has been described in "New Approaches to Acne Treatment" by W. J. Cunliffe, ed. Martin Dunitz, London, 1989.
Acne vulgaris is a chronic disorder of the pilosebaceous follicles (apparatus) characterized by comedones (blackheads), papules, pustules, cysts, nodules, and often scars, that appear on the most visible areas of the skin particularly on the face, chest, back and occasionally neck, and upper arms.
The pilosebaceous apparatus is largely under the control of endogenous hormones (mainly androgens) which are present in unusually high concentrations in the blood during adolescence and puberty giving rise to an excessive production of sebum. The condition may worsen by a simultaneous increase in the rate of keratinization of the skin's horny layer (the stratum corneum). As the horny cells proliferate, they can form an occlusive plug or comedone which coupled with the increased production of the sebum, represents an ideal medium for the proliferation of the skin resident strains, such as the Gram positive anaerobic bacterium, Propionibacterium acnes.
Eventually, the plugged follicles rupture and allow the discharge of their contents causing local swelling and inflammation. The exposed follicles may darken from the deposition of pigment from damaged cells in the deeper layer of skin.
Acne is a multistage condition and in most severe form leads to hospitalization of the patient and extensive discomfort with long term scarring of the skin. There is a need for improved treatments for acne that will effectively prevent the condition developing to its most severe form and that can be used by majority of the sufferers without adverse effects.
At this time there are numerous treatments available for treating acne but each treatment has unfortunate limitations which it would be desirable to overcome. In most part, treatment of acne is by topical formulations in the form of creams, gels, emulsions or lotions which contain selected agents. These agents include hormones or hormone agonists and antagonists (EP A1 0 563 813 and U.S. Pat. No. 5,439,923), antimicrobial agents (U.S. Pat. No. 4,446,145, GB 2,088,717, GB 2,090,135, GB 1,054,124, U.S. Pat. No. 5,409,917), salicylic acid (U.S. Pat. No. 4,514,385, U.S. Pat. No. 4,355,028, EP A1 0 052 705, FR-A 2,581,542, and FR-A 2,607,498). The problems associated with topical treatment of acne with creams, gels, emulsions and lotions include the lack of precision of application and associated lack of control over precise dose at the target site. Application of a cream, gel, emulsion or lotion results in exposure of an area considerably in excess of that covered by lesion thereby exposing normal healthy skin to the anti-acne formulation. For example salicylic acid is an irritant to normal skin over prolonged exposure and particularly in high concentrations.
Oral administration of anti-acne agents is currently provided for severe cases of acne. These are reviewed in "Acne, A Review of Optimum Treatment" by Sykes N. I. and Webster G. F in Drugs 48, 59-70 (1994). Numerous side effects have been described using oral administration of anti-acne drugs. For example, isotretinoin which is a derivative of vitamin A has associated risks of teratogenicity and may be a risk for women of childbearing age. Oral administration of antibiotics suited for treating acne, may induce the appearance of adverse effects which include abdominal cramps, black tongue, cough, diarrhea, fatigue, irritation of the mouth and other undesirable symptoms.
Salicylic acid in the form of a tacky hydrophilic gel dressing (U.S. Pat. No. 5,258,421) and in combination with pantothenic acid or pantothenic acid derivative in a cleansing pad (PCT WO 93/21899) has been used for treating acne.
In addition, a patch containing cephalosporin has been described in the U.S. Pat. No. 5,409,917 for the treatment of acne using a method for making nicotine patches. Since the patch was not optimized for the special circumstances associated with acne including optimizing the anti-acne agent content and placement of the patch at multiple locations on exposed skin such as the face, the patch has not been adopted as an anti-acne formulation delivery modality.
There is a need therefore for methods and devices for treating patients with acne that have minimum adverse effects, have maximum efficacy and may be simple and comfortable to use.